Question 623: Current Electricity

Question

A certain wire $$\mathrm{A}$$ has resistance $$81 ~\Omega$$. The resistance of another wire $$\mathrm{B}$$ of same material and equal length but of diameter thrice the diameter of A will be :

Accepted Answer

$$\mathrm{R=\frac{\rho L}{A}}$$
If diameter becomes thrice then cross section area will become 9 times so
$$\mathrm{R\propto \frac{1}{A}}$$
Resistance will become $$\frac{1}{9}$$ times
$$\mathrm{R'=\frac{81\Omega}{9}=9\Omega}$$

Answer

$$81 ~\Omega$$

Answer

$$9 ~\Omega$$

Answer

$$729 ~\Omega$$

Answer

$$243 ~\Omega$$

Current Electricity

A certain wire $\mathrm{A} has resistance 81 ~\Omega. The resistance of another wire \mathrm{B}$ of same material and equal length but of diameter thrice the diameter of A will be :

Choose the correct answer: